There are known distance sensors in which an infrared beam is irradiated from an illumination device onto a physical object, an image of the physical object is captured by an image capture module equipped with an image capture element, and the distance to the physical object is detected based on image data thereby obtained. The image capture module installed in such a sensor comprises a lens unit equipped with a band-pass filter for transmitting returning light of the infrared beam radiated by the illumination device from among the light reflected by the physical object, leading the returning light to the image capture element, and blocking light beams of all other wavelength bands. The band-pass filter is an interference filter in which a multilayer film is formed on the surface of a transparent substrate. Patent Document 1 discloses an interference filter for transmitting light beams of a prescribed wavelength band of the infrared region.